(1) Field of application
The present invention relates to core-making machines, and more particularly, to an apparatus for the production of cores from fluidized sands in hot boxes.
The machine of the invention may be used at mass-production plants of, for example, the sanitary engineering industry, automobile industry, electrical engineering and machine-building industries.
Core-making processes based on hot-box and cold-box techniques are in wide use today. However, the equipment employed for performing these techniques fail to provide satisfactory solution to the problems of enhancing production efficiency, increasing the strength of a sand mixture, and improving working conditions. The reason for this is ineffective ventillation of cores, especially such that are used in heating boilers and radiators and enclosed in metal, having, with the exception of two small core print holes, no contact with a mould. Since the hardening of a sand takes place uniformly throughout the cross section, the cores are made up of two pieces, which are subsequently glued together, whereby a vent is provided inside the core to communicate the latter with the atmosphere. Needless to say that additional technological operations render the core-making process much more complicated, labour- and time-consuming, as well as impossible for adaptation to automatic performance. In addition, dimensional accuracy of the cores thus produced is impaired along with their quality.
(2) Description of the prior art
There is known a simple method of making cores, which consists in that a fluidized sand is packed under pressure in a hot core box, which then is sealed, and the sand is held therein for a preset time required for the sand to harden, whereupon the box is opened and a finished core is removed therefrom (cf. U.S. Pat. No. 3,802,484, cl. 164-169).
The above method is suitable for the production of any type of cores made in a single piece, since natural vents or porosity are formed in the interior of each core to permit effective ventillation of gases.
There is known an apparatus for making cores in accordance with the prior-art method, also described in the patent referred to above.
The apparatus in question comprises vessels and feeders for metering initial sand components, a mixer with a gate adapted to close its outlet, an injection cylinder with a plunger, a proportioning chamber, a slide with a telescopic piston, and a lifting platform. The apparatus is operated in the following manner.
Initial components of a sand mixture are fed to a mixer to be properly intermixed therein. The fluidized sand thus prepared is then passed through the outlet into the proportional chamber which is closed from the bottom by the slide. Once the proportioning chamber is filled, the gate closes the mixer outlet, the slide is actuated to bring the nozzle in alignment with the proportioning chamber, and the lifting table is operable to raise the hot core box, forcing it against the nozzle. Under the action of the injection cylinder, the plunger performs compacting of the sand in the core box. On completion of the packing operation, the core box is sealed to thereby prevent the sand from being forcibly discharged through the outlet of the core box. After a period of time required for the foam to settle and for the sand to loose its flowability, the core box is transferred onto another station. The slide is again actuated to close the proportioning chamber from the bottom and the sand leftovers are removed therefrom. The plunger is lifted to occupy its initial position, and the gate is actuated to open the mixer outlet. The operating cycle is then resumed.
Under certain conditions, pressure is increased in the core box to reach a value sufficient to overcome the weight of the top section of each core box. If, however, the core box is not held joined together for an appropriate time at the packing station on completion of packing and sealing, then its top section will be raised to permit the discharging of sand to take place at its parting, which will inevitably lead to the production of a defective core.
On the other hand, an extensively long period of time, during which the core box is held between the lifting table and the packing device so as to ensure a drop in pressure preventing the uplifting of the core box section on completion of the disjoining operation, adversely affects production efficiency of the core-making machine and, in the final count, fails to completely eliminate vertical vibrations of the core box top section due to occur under the effect of residual pressure. The result of such vibrations is impaired dimensional accuracy and, consequently, poor quality of the core being produced.
There is known an apparatus for making cores from fluidized sands in hot boxes, which comprises a support frame mounting a transport means and, arranged in the direction of the technological process, a device for the preparation of a fluidized sand, an appliance for packing the sand in core boxes whose top and bottom sections are joined and disjoined by appropriate mechanisms, a device for separation of core boxes, and an arrangement for the delivery of finished cores (see, for example, patent application No. 2,057,318 laid out with the Patent Office of Great Britain on Apr. 1, 1981, the inventors of which are partially the same as of the present application).
The above-mentioned apparatus comprises a heating chamber mounted on the support frame between the packing mechanism and the core separating device, and a pusher operable to move the core boxes through the heating chamber.
The device for separation of core boxes includes a mechanism for punching the cores in the core boxes, and the transport means made in the form of a floor conveyer co-operating with the packing mechanism via a transfer table and with the core-box separating device via a second transfer table.
In the apparatus described above the mechanisms for joining and disjoining top and bottom sections of each core box are built in the core boxes and are actuated by individual drives which are arranged before the heating chamber and behind it, if viewed in the direction of the technological process.
The actuator of the core-box joining mechanism is made in the form of an air cylinder. The core-box disjoining mechanism is connected with brackets having adjustable stops.
The core-box joining and disjoining mechanisms incorporate two horizontal bars with tapered members which are positioned in its lower part and interact with the drives, and two vertical bars fixed on its upper part and each having one of its ends formed with slits and tapered holes permitting co-operation with the tapered members of the horizontal bars.
The above-described apparatus is operated as follows.
The first transfer table is actuated to lift a hot box from the transport means and delivers it to the sand packing device. One of the drives is operable to act on the horizontal bars, positioned in its lower part, so that the tapered members are received in the tapered holes provided in the vertical bars which are disposed in its upper part. In this way the top and bottom sections of a core box are reliably joined together. This operation renders it unnecessary to hold the core boxes at the after-packing station and thus makes it possible to substantially reduce the operating cycle of the apparatus.
The packing mechanism is operable to compact the sand in the core box, which is first sealed and then delivered by the pusher to the heating chamber. As the next core box is brought to the heating chamber, the preceding box is brought out of the latter to be thereafter handled by the mechanism for delivering a finished core. The mechanism in question is operable to drag the core box onto the second transfer table. Towards the end of travelling, the horizontal bars of the core box, positioned in its lower part, are acted upon by another drive to be thereby returned to initial position. As a result, the top and bottom sections of the core box are brought apart and the core box is disjoined. The tapered members of the horizontal bars are brought out of the tapered holes in the vertical bars. As this happens, the core box is depressurized. The separation device is operable to open the core box, and the vertical bars positioned in the top section of the box are disengaged from the horizontal bars which are disposed in the bottom section of the core box. The operation of disengagement is carried out unhinderedly due to the provision of slits.
After a finished core has been removed from the core box, the latter is reassembled by means of the separating device and then is lowered by the second transfer table on to the conveyor means operable to return the core box to the packing station.
The fact that the core-box joining and disjoining mechanisms are built into the core box and, therefore, depend on its construction, render it oftentimes difficult, if not impossible, reliable joining and disjoining of the top and bottom sections of each core box.
In addition, the provision of drives co-operating with the core-box joining and disjoining mechanisms makes the apparatus complicated in construction and impair its operating reliability.